Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Bacterial Structures”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20Linked to original sources
PubMed2004

Cutting edge: innate immune system discriminates between RNA containing bacterial versus eukaryotic structural features that prime for high-level IL-12 secretion by dendritic cells.

RNA derived from bacterial but not eukaryotic sources, when transfected into human monocyte-derived dendritic cell precursors, induces high-level IL-12 secretion in conjunction with dendritic cell maturation stimuli. In vitro-transcribed mRNA that mimics the structure of bacterial mRNA in the lack of a long 3'-poly(A) tail likewise induces IL-12 secretion, but this property is lost upon efficient enzymatic 3'-polyadenylation. Among other tested RNAs, only polyuridylic acid induced IL-12 p70. This RNA response phenomenon appears biologically distinct from the classically defined response to dsRNA. RNA-transfected APC also polarize T cells in an IL-12-dependent manner toward the IFN-gamma(high)IL-5 (low) Th1 phenotype, suggesting a link between the detection of appropriately structured RNA and the skewing of immune responses toward those best suited for controlling intracellular microbes. RNA structured to emulate bacterial patterns constitutes a novel vaccine strategy to engender polarized Th1-type immune responses.

3' Untranslated Regions↗
PubMed2002

Functional and structural adaptations of bacterial communities growing on particulate substrates under stringent nutrient limitation.

Biomass recycle reactors (BRRs) were used as a model system to study the functional and structural adaptations of mixed bacterial communities in response to the imposition of increasingly severe nutrient limitation. BRRs were fed synthetic media containing either spinach homogenate or autoclaved yeast cells to simulate the complex mixtures of particulate carbon sources that are often present in nature. In the BRRs fed spinach homogenate, the biomass (measured as particulate protein) exhibited a physiological response similar to previous studies as detected by 40-80% reductions in respiratory potential and by relatively stable catabolic ectoenzyme activities. Concomitant adaptations in bacterial community structure were detected by PCR-DGGE and RT-PCR-DGGE of 16S rDNA and 16S rRNA fragments, respectively. The microbial community structure was dynamic even after the biomass had reached a quasi-steady state with respect to physiological measurements. In the BRRs fed yeast cells, respiratory potentials increased 2- to 5-fold during the initial portion of the BRR run and alpha-glucosidase and beta-glucosidase activities increased 2- to 4-fold. Substantial bacterial community shifts were also detected in both the rDNA and rRNA profiles, indicating that this community was also structurally dynamic. These experiments suggest that phylogenetically different bacteria sustained the functional activities in these ecosystems in response to increasingly stringent nutrient limitation.

Bacteria↗
PubMed1984

Inhibition of ribonuclease contamination in preparations of T4 RNA ligase, polynucleotide kinase, and bacterial alkaline phosphatase with bentonite.

Commercial preparations of the enzymes used in the analysis of RNA primary structure (bacterial alkaline phosphatase, polynucleotide kinase, and RNA ligase) are virtually always more or less contaminated with RNases. This leads to degradation of initial RNAs in the course of labeling and formation of a set of spurious labeled fragments. We have shown that bentonite present in the incubation medium in a concentration of 0.04% selectively inhibits the contaminating RNases, not affecting the activities of bacterial alkaline phosphatase, polynucleotide kinase, and RNA ligase.

Alkaline Phosphatase↗
PubMed2000

[Cell division genes and proteins in bacterial cells].

In this review, genes and proteins involved in cytokinesis and cell proliferation of cell-wall bacteria and mycoplasms are considered. We hope that this comparative analysis of genes and proteins of phylogenetically distant bacteria, including the minimal cells of mycoplasmas, can be useful for understanding the basic principles of prokaryotic cell division. The ftsZ gene was found among representatives of all bacterial groups. The recent data indicate that FtsZ protein plays the central role in the process of bacterial cell division. FtsZ protein was revealed in all Eubacterial groups (including mycoplasmas), in Archaebacteria and chloroplasts, All FtsZ proteins are able to form protofilaments as a result of polymerization in vitro and demonstrate GTF-ase activity. On the base of these properties and some similarities in amino acid sequences with tubulins, it has been suggested that FtsZ protein is an evolutionary ancestor of Eukaryotic tubulins. On the earliest stage of bacterial cytokinesis FtsZ protein assembles into a submembranous Z-ring which encircles bacterial cell in the predivisional site. Some other bacterial proteins take part in stabilization and contraction of the Z-ring, which is considered as a cytoskeleton-like bacterial structure.

Bacteria↗
PubMed1996

Paleomicrobiological study in dental calculus: Streptococcus mutans.

Morphological types of bacterial remains preserved in ancient tartar of teeth from extinct human groups, which included some communities of coastal gatherers, fishermen, hunters, and farmers, and those practicing a mixed economy, were analyzed. Previous studies have shown the presence of bacteria in ancient tartar. The aim of this work was to determine whether Streptococcus mutans was present in ancient populations (500-12,000 years old). Teeth samples were from ancient skulls obtained from different anthropological collections: the north and south of Chile (before the Spanish conquest), Palencia, Spain, and an eastern Mediterranean region (Levant). Optical microscopy showed Gram positive and Gram negative bacteria. Scanning electron microscopy identified morphological types of bacteria. Transmission electron microscopy enabled categorization of bacterial structures. Fluorescence microscopy helped label and identify S. mutans, using polyclonal antibodies. Bacterial morphotypes were related to different subsistence patterns. Hunters, fishermen, and gatherers had a less diverse flora with bacillary and coccal morphotypes. Agricultural groups showed greater diversity with additional filamentous and spiral morphotypes. The best preserved ultrastructural feature was the cell wall. The existence and colonization capacity of the mutans-like streptococci preserved in tartar was established for the ancient populations studied, with the exception of Cerro Sotta (south of Chile). Hence, their occurrence could not be related to diet or subsistence pattern.

Antibodies, Bacterial↗
PubMed2001

Structural characterization of the N-terminal oligomerization domain of the bacterial chromatin-structuring protein, H-NS.

The H-NS protein plays a key role in condensing DNA and modulating gene expression in bacterial nucleoids. The mechanism by which this is achieved is dependent, at least in part, on the oligomerization of the protein. H-NS consists of two distinct domains; the N-terminal domain responsible for protein oligomerization, and the C-terminal DNA binding domain, which are separated by a flexible linker region. We present a multidimensional NMR study of the amino-terminal 64 residues of H-NS (denoted H-NS1-64) from Salmonella typhimurium, which constitute the oligomerization domain. This domain exists as a homotrimer, which is predicted to be self-associated through a coiled-coil configuration. NMR spectra show an equivalent magnetic environment for each monomer indicating that the polypeptide chains are arranged in parallel with complete 3-fold symmetry. Despite the limited resonance dispersion, an almost complete backbone assignment for 1H(N), 1H(alpha), 15N, 13CO and 13C(alpha) NMR resonances was obtained using a suite of triple resonance experiments applied to uniformly 15N-, 13C/15N- and 2H/13C/15N-labelled H-NS1-64 samples. The secondary structure of H-NS1-64 has been identified on the basis of the analysis of 1H(alpha), 13C(alpha), 13Cbeta and 13CO chemical shifts, NH/solvent exchange rates, intra-chain H(N)-H(N) and medium-range nuclear Overhauser enhancements (NOEs). Within the context of the homotrimer, each H-NS1-64 protomer consists of three alpha-helices spanning residues 2-8, 12-20 and 22-53, respectively. A topological model is presented for the symmetric H-NS1-64 trimer based upon the combined analysis of the helical elements and the pattern of backbone amide group 15N nuclear relaxation rates within the context of axially asymmetric diffusion tensor. In this model, the longest of the three helices (helix 3, residues 22-53) forms a coiled-coil interface with the other chains in the homotrimer. The two shorter N-terminal helices fold back onto the outer surface of the coiled-coil core and potentially act to stabilise this configuration.

Bacterial Proteins↗
PubMed1983

Invited review: bacterial flagellar sheaths: structures in search of a function.

Although bacterial flagellar sheaths were observed over 30 years ago, they may still be characterized as structures in search of a function. In addition to true sheaths, bacterial flagella may possess other adornments that cause an increase in the organelle's cross-sectional diameter. These "complex flagella" are sharply differentiated from sheathed flagella. Immunological and chemical distinctions have been found between flagellar sheaths, flagellar cores, and LPS layers inferred to be the sheath sensu stricto. Although complex flagella may serve as specific receptors for flagellotropic phages or in allowing for more efficient swimming in viscous environments, similar functions have not yet been attributed to true sheaths. It is postulated that flagellar sheaths may allow for specific interaction between a bacterium and a surface. In addition, there is a problem as to the relationship between a rapidly rotating flagellum and the sheath.

Antigens, Bacterial↗
PubMed1992

The interaction of macrophages and bacteria: Escherichia coli species, bacterial lipopolysaccharide, and lipid A differ in their ability to induce tumoricidal activity and the secretion of reactive nitrogen intermediates in macrophages.

The ability of nine Escherichia coli strains, and of bacterial lipopolysaccharide (LPS)3 and lipid A preparations, to elicit in a pure population of bone marrow-derived mononuclear phagocytes (BMM phi) tumoricidal activity and/or the generation of reactive nitrogen intermediates (RNI) was compared. Generally, low concentrations of E. coli organisms were able to trigger the generation of RNI: however, for induction of tumoricidal activity, higher concentrations were required. Nonisogenic E. coli species exhibited different ability; isogenic E. coli organisms that differed only in the expression of K antigen exhibited similar ability to elicit the macrophage activities. LPS proved to be highly efficient in triggering the secretion of reactive nitrogen intermediates; lipid A was clearly less potent, but evidence is presented to suggest that this was due to the diminished solubility of these reagents. On the other hand, all LPS and lipid A samples were very poor inducers of tumoricidal activity. Although RNI secretion and expression of tumoricidal activity are both strongly dependent on L-arginine, various evidence suggests that the two functions are not closely correlated and are induced by different bacterial structures.

Animals↗
PubMed2005

Structures of the bacterial ribosome at 3.5 A resolution.

We describe two structures of the intact bacterial ribosome from Escherichia coli determined to a resolution of 3.5 angstroms by x-ray crystallography. These structures provide a detailed view of the interface between the small and large ribosomal subunits and the conformation of the peptidyl transferase center in the context of the intact ribosome. Differences between the two ribosomes reveal a high degree of flexibility between the head and the rest of the small subunit. Swiveling of the head of the small subunit observed in the present structures, coupled to the ratchet-like motion of the two subunits observed previously, suggests a mechanism for the final movements of messenger RNA (mRNA) and transfer RNAs (tRNAs) during translocation.

Binding Sites↗
PubMed1992

Microfossils and possible microfossils from the Early Archean Onverwacht Group, Barberton Mountain Land, South Africa.

There is widespread textural evidence for microbial activity in the cherts of the Early Archean Onverwacht Group. Layers with fine carbonaceous laminations resembling fossil microbial mats are abundant in the cherty metasediments of the predominantly basaltic Hooggenoeg and Kromberg Formations. In rare cases, filamentous microfossils are associated with the laminae. The morphologies of the fossils, as well as the texture of the encompassing laminae suggest an affinity to modern mat-dwelling cyanobacteria or bacteria. A variety of spheroidal and ellipsoidal structures present in cherts of the Hooggenoeg and Kromberg Formations resemble modern coccoidal bacteria and bacterial structures, including spores. The development of spores may have enabled early microorganisms to survive the relatively harsh surficial conditions, including the effects of very large meteorite impacts on the young Earth.

Carbon↗
PubMed1981

Pathogenesis of acute bacterial diarrheal disorders.

Acute bacterial diarrheal disease is a worldwide problem of enormous magnitude. In recent years a number of bacteria have been added to the list of recognized etiologic agents causing acute diarrheal disease. This was made possible by our increased understanding of the mechanisms by which such bacteria cause diarrhea and by the development of methods to detect these bacterial enteropathogens. We are now able to define an etiologic agent in 50-80% of cases of acute diarrhea, depending on the particular population. The bacterial agents recently incriminated as important causes of diarrhea include E coli Y. enterocolitica, B. cereus, C. fetus, V. parahemolyticus, and many other coliform organisms. Establishment of an enteric infection depends upon a complex interplay between host defense mechanisms and bacterial virulence factors adapted to overcome these defenses. Bacterial enteropathogens cause diarrhea primarily by elaborating enterotoxins (which also requires the organisms to adhere to the surface of the intestinal cell) and by invading the intestinal mucosa. The number of known bacterial enterotoxins has rapidly increased. Enterotoxins cause intestinal secretion and diarrhea by stimulating the adenyl cyclase system or the guanyl cyclase system and by other mechanisms yet to be defined. The ability of enterotoxigenic bacteria to adhere to the intestine involves a specific binding interaction between bacterial structures called pili or fimbriae and specific receptors on the surface of intestinal cells. Both bacterial pili and the intestinal receptors are under genetic control. A variety of other bacteria, Salmonellae, Shigellae, Y. enterocolitica etc, must invade the mucosa to cause diarrheal disease. The ability to invade is essential to the pathogenesis of disease and requires particular surface characteristics of the bacterium as well as the active participation of both the bacterium and the host cell. The bacteria probably elaborate substances that signal the host cell to initiate the invasive process, i.e. endocytosis. The mechanism by which invasive bacteria evoke intestinal secretion is uncertain but is probably a multifactorial process involving products elaborated by the mucosal acute inflammatory reaction and enterotoxins elaborated by the bacteria.

Acute Disease↗
PubMed1998

Binding to human extracellular matrix by Neisseria meningitidis.

Adhesion of Neisseria meningitidis strains to extracellular matrix (ECM) and purified matrix components was examined. Most strains bound to subendothelial ECM as well as to immobilized fibronectin and types I, III, and V collagen. Strains from healthy carriers adhered significantly better than isolates from patients. The binding site was localized to the central 75-kDa cell-binding domain of the fibronectin molecule. This domain has not been described previously to interact with bacterial structures.

Bacterial Adhesion↗
PubMed1992

[The etiological structure of acute bacterial meningitis in different regions].

In 1985-1989 the etiological structure of acute bacterial meningitides (ABM) in children was studied in 4 largest industrial cities in different regions of the European part of the former USSR, as well as in 2 industrial cities of western Siberia. Due to the common methodological approach used in all investigations, comparable data were obtained in all cities. These investigations revealed that meningococci caused 53.0-86.7% of all cases of ABM in children, which corresponded to moderately increased morbidity rate in meningococcal infection (3.9-11.0 cases per 100,000 of the population, mostly 5.0-7.0 cases) in these cities with its progressive decrease during 3-4 years of observation. The gradual change of meningococci from group A, prevailing in the '70s and early '80s, to group B and in some cases the appearance of group C meningococci, accompanied by a decrease in morbidity rate, were noted. In St. Petersburg the indices of ABM morbidity in children aged up to 5 years for 1987 and 1988, caused by Haemophilus influenzae (0.74 and 4.13) and pneumococci (3.23 and 4.86), could be calculated. A great number of ABM cases of unclear etiology (15.9-33.3%) suggests that the number of ABM cases caused by these two infective agents was underestimated.

Acute Disease↗
PubMed1990

Separation of sublethal and lethal effects of the bactericidal/permeability increasing protein on Escherichia coli.

Binding of the bactericidal/permeability increasing protein (BPI) of granulocytes to Escherichia coli promptly produces several discrete outer envelope alterations and growth arrest without major impairment of bacterial structure or biosynthetic capabilities, raising the question whether these early effects of BPI are sufficient to cause bacterial death. In this study, the bactericidal action of BPI was examined more closely. We have found that bovine or human serum albumin blocks bacterial killing without preventing BPI binding or an increase in outer membrane permeability. Moreover, addition of serum albumin after BPI results in growth resumption without displacement of bound BPI and without (early) repair of the envelope alterations. These effects are opposite to those produced by Mg2+ (80 mM), which displaces greater than 85% of bound BPI and rapidly initiates outer envelope repair without restoration of bacterial growth. The extent of rescue by serum albumin depends on the time and pH of preincubation of BPI with E. coli: e.g., for E. coli J5 treated with human BPI, t1/2 = 79 min at pH 7.4 and 10 min at pH 6.0. The serum albumin effects on BPI action are the same in wild-type E. coli and in a mutant strain lacking an activatable phospholipase, indicating that serum albumin does not act by sequestering membrane-damaging products of bacterial phospholipid hydrolysis. The progression from reversible to irreversible growth arrest, revealed by the subsequent addition of serum albumin at different times, is paralleled by a decrease in amino acid uptake and an increase in the permeability of the cytoplasmic membrane to o-nitrophenyl-beta-D-galactoside. These findings demonstrate at least two stages in the action of BPI: (a) an early, reversible, sublethal stage in which BPI has effects on the outer envelope and causes growth arrest, and (b) time- and pH-dependent progression to a lethal stage, apparently involving cytoplasmic membrane damage, possibly caused by penetration of a small subpopulation of BPI.

Animals↗
PubMed1999

Formation and structure of mixed bacterial communities.

Mixed bacterial communities are formed by unrelated bacteria on solid media. Mixed bacterial communities on solid media are similar to "classical" colonies and are formed after the growth of a large number of unrelated bacteria simultaneously plated onto a limited area of agar. The morphology of the mixed bacterial communities was similar for different combinations of bacteria and did not change when the bacteria were plated on different media. Different bacterial strains form zones of individual and mixed growth in the structure of mixed bacterial communities. The results of electron microscopic examination indicate that mixed bacterial communities are isolated from their external environment by a surface film. The basic part of this film is formed by an elementary membrane. The membrane of the surface film of mixed bacterial communities is a stable structure occupying a large surface area. The results of this investigation seem to indicate the existence of a special type of co-operation between different species of bacteria. This type of co-operation may be very important in the regulation of interactions between different bacteria and between bacteria and the environment.

Bacillus cereus↗
PubMed2000

The natural product capsaicin inhibits photosynthetic electron transport at the reducing side of photosystem II and purple bacterial reaction center: structural details of capsaicin binding.

Capsaicin, a natural quinone analog, was found to block electron transport, in both plant photosystem II (PSII) and bacterial reaction center (RC) from Rhodobacter sphaeroides, at the QB site. The mode of action of capsaicin was investigated by O2 evolution measurements and fluoresence induction studies in the case of PSII, and flash-induced absorbance spectroscopy in the case of the bacterial RC. Structural details of capsaicin binding to the bacterial RC complex were determined by X-ray crystallographic analysis.

Binding Sites↗
PubMed1976

Nonspecific complement activation by streptococcal structures. I. Re-evaluation of HLA cytotoxicity inhibition.

A number of experiments have suggested that there is an antigenic relationship between the HLA complex and streptococcal bacterial structures. Using inhibition of cytotoxicity of HLA antisera as our assay system, it was demonstrated that the inhibitory effect on HLA cytotoxicity by streptococcal antigens is, in reality, due to activation and consumption of components of the alternate complement pathway. In addition, antisera prepared against streptococcal membrane antigens had no cytotoxic effect on a large panel of human lymphocytes, nor did these antisera exhibit immunofluorescent staining of lymphocytes directly. These experiments are compatible with our concept that the HLA complex may have evolved through selective evolutionary pressure as a means of escaping bacterial mimicry.

Antibodies, Bacterial↗
PubMed2004

The bacterial flagellar motor: structure and function of a complex molecular machine.

The bacterial flagellar motor harnesses ion flow to drive rotary motion, at speeds reaching 100000 rpm and with apparently tight coupling. The functional properties of the motor are quite well understood, but its molecular mechanism remains unknown. Studies of motor physiology, together with mutational and biochemical studies of the components, place significant constraints on the mechanism. Rotation is probably driven by conformational changes in membrane-protein complexes that form the stator. These conformational changes occur as protons move on and off a critical aspartate residue in the stator protein MotB, and the resulting forces are applied to the rotor protein FliG. The bacterial flagellum is a complex structure built from about two dozen proteins. Its construction requires an apparatus at the base that exports many flagellar components to their sites of installation by way of an axial channel through the structure. The sequence of events in assembly is understood in general terms, but not yet at the molecular level. A fuller understanding of motor rotation and flagellar assembly will require more data on the structures and organization of the constituent proteins.

Bacteria↗